Turbocharged engine including an engine driven supercharger

A multiple compressed air supply system comprising:

• an engine including a power output;
• an air supply passage for conducting air to said engine;
• an exhaust gas passage for conducting exhaust gas from said engine;
• an air supercharger including an air inlet and an air outlet, said air outlet communicating with said air supply passage by means of an air bypass said supercharger including a disengageable clutch operably connected to said power output to enable said supercharger to be driven by said engine when said clutch is engaged;
• a turbocharger including a turbine disposed in said exhaust gas passage for being driven by engine exhaust gas and an air compressor driven by said turbine,
• said compressor disposed in said air supply passage downstream of said supercharger,
• pressure sensing means for detecting pressures at an inlet and an outlet of said compressor;
• an exhaust gas bypass interconnecting portions of said exhaust gas passage disposed upstream and downstream of said turbine;
• adjustable control valve means for regulating the amount of air flowing through said air bypass;
• adjustable wastegate valve means for regulating the amount of exhaust gas flowing through said exhaust gas bypass;
• and
• control means operably connected to said pressure sensing means, said clutch means, and said control valve means for:
• engaging said clutch and closing said control valve means when said engine is operated in a low speed range,
• engaging said clutch and partially opening said control valve means when said engine is operated in an intermediate speed range for maintaining the air pressure at said compressor outlet to be no greater than a first preset value, and
• fully opening said control valve means when said engine is operated in a high speed range, and for disengaging said clutch when a differential pressure between said compressor inlet and outlet reaches a second preset value,
• said control means being operably connected to said wastegate valve means for opening said wastegate valve means to control the operation of said turbine in a manner maintaining compressor outlet pressure no higher than said first preset value when said engine is operated in said high speed range and said clutch is disengaged.